The present invention relates to the use of a paste to make inherently coherent dried granules of sterically hindered phenol antioxidants. The dried granules have a balanced hardness suitable for both handling and incorporation into a polymer composition. The granules may be agglomerates, which typically are spherical in shape, or they may be cylindrical or elongated pellets.
Organic polymers, in particular polyolefins such as polyethylene and polypropylene, commonly are known as xe2x80x9cplastics.xe2x80x9d Various additive systems are used during the processing of plastics in order to assure that the plastic product has long term stability and desired service properties. Additives and stabilizers prevent the plastic product from being damaged by light, heat, and by residues of the catalyst system used to produce the plastic.
The additives and stabilizers may be used individually, or in an additive xe2x80x9csystemxe2x80x9d that includes a mixture of components. Common additive systems include sterically hindered phenol antioxidants in combination with a secondary phosphite antioxidant and/or an acid neutralizer.
Sterically hindered phenol antioxidants generally are fine powders that present dusting and other handling problems, as well as separation tendencies that cause metering difficulties. In the past, these problems have been solved by adding extraneous binders to the additive system. Exemplary binders used for such purpose include fatty acids and their salts, such as calcium stearate. The disadvantage of using an extraneous binder is that the binder remains as a contaminant in the final additive system.
Additive systems are needed which solve the handling problems for sterically hindered phenols, but which do not introduce contaminats into the final additive system.
The present invention solves the foregoing problem by providing a compound comprising
a powder comprising an additive system comprising at least one sterically hindered phenol antioxidant; and, an organic processing agent comprising at least one friability reduction agent. The invention also is directed to a compound consisting essentially of one or more dried granules consisting essentially of an additive system comprising at least one sterically hindered phenol.